Nuclear Detection: Are Taxis the Answer to an Effective Detection Strategy in Manhattan and Other US Cities?

Terrorist nuclear attack is a potentially devastating threat to homeland security. It is increasingly important to have the capability to intercept illicit nuclear materials entering the country and to monitor for nuclear threats emerging from within. One way to detect nuclear materials in cities is by using a fleet of mobile sensors that could be installed, for example, in taxis.

The nuclear and radiological materials whose detection is of particular concern are radiation dispersion devices (RDDs) – more commonly known as dirty bombs – and special nuclear materials (particularly highly enriched uranium and weapons-grade plutonium) that could provide the fissile material for a nuclear weapon.

The need to distinguish true threats from commonly occurring benign sources and background sources of radiation is a particular challenge in nuclear detection.

Major metropolitan areas present attractive targets, but cover large geographic areas that may be difficult to monitor and/or patrol. They present many of the same challenges as special events, but on a grander scale – both in terms of geographic area and duration.

CCICADA is a Department of Homeland Security University Center of Excellence that focuses its research and education on data analytics. “In CCICADA’s early work on nuclear detection, we did not have a specific model of vehicle movement,” says Fred Roberts, Director of CCICADA. “We assumed that vehicles are randomly moved to new locations in the region being monitored each time period. If there are many vehicles with sufficiently random movements, this is a reasonable first approximation.”

Big city police departments, like New York City, have started experimenting with putting nuclear detectors in police cars. CCICADA set out to determine if there are enough police cars to give “adequate” coverage to have a high probability of finding a nuclear device.

The required number of vehicles in the surveillance network can be determined by statistical power analysis. The larger the number of vehicles, the higher is the potential power of detection.

CCICADA concluded that Manhattan would need 4,000 vehicles equipped with nuclear-detection sensors to even get 75% power.

The NYC Police Department has more than 3000 vehicles in 76 precincts in 5 boroughs. Perhaps 500 to 750 are in streets of Mid/Downtown Manhattan at one time. This would not be enough police cars to provide given even 30 percent detection power. Clearly, there are not enough police cars to accomplish the required coverage.

Another problem is that police cars tend to remain in their own region/precinct. They don’t drive around randomly, and randomness is needed so an adversary can’t anticipate detection.

But maybe there are enough taxis? “Our models show that there are,” says Roberts. “The challenge now is to educate police to the advantages of using taxicabs.”

He added that to do this, CCICADA and its homeland security partners will need to create new and better communication and interrelationships between police security operations and taxicab drivers.